1. Field of the Invention.
The present invention relates to an improvement in prosthetic dentistry. More particularly, the invention relates to the art of forming an acid-etched surface on a porcelain veneer facing using an aqueous acidic solution and subsequently forming a product comprising a porcelain veneer facing bonded directly to a natural or virgin tooth without requiring the conventional grinding and capping procedures and without requiring significant reduction of the tooth surface.
2. Description of the Prior Art.
At the present time, probably the most common technique for covering a discolored or disfigured tooth is to grind the tooth down to a stub or post and then affix a tooth "cap" onto the post, the cap often consisting of porcelain bonded to gold. This technique, however, is undesirable, particularly in the case of children, because it requires that the natural or virgin tooth largely be removed in its preparation for receipt of the cap.
In attempt to overcome the disadvantages of grinding, certain plastic shells have been used to cover discolored or disfigured teeth. The most common commercially used plastic materials for modifying an individual's tooth arrangement or disfigurement have been various types of thermoplastic resins. These materials usually come as ready-to-use plastic shells which slip over the patient's tooth and are attached thereto by a suitable adhesive after acid-etching the virgin or natural tooth surface. Alternatively, the plastic resin material has been applied as a loose composite medium which is grossly applied to the tooth surface and thereafter ground, shaped and polished in the oral chamber. These plastic materials, however, suffer from many other disadvantages, such as their tendency to absorb water, discolor, wear down and cause gum tissue irritation. Consequently for example, the use of plastic shells or veneer facings has been primarily restricted to the relatively short term requirements of covering discolorations in the "baby" teeth of small children.
Porcelain has long been considered the ideal material for preparing prosthetic dental devices since it is the material which most closely resembles natural or virgin teeth. However, because of the extreme surface imperviousness of porcelain, it has heretofore been unknown, and thought to be impossible, to securely fix a porcelain veneer facing to a natural or virgin tooth. In particular, it has heretofore been found that the conventional methods of acid-etching or grinding down of the natural tooth were unsatisfactory because the porcelain veneer facing tended to slip off and become dislodged when subjected to a normal amount of masticatory stress.
Prior to the instant invention, it was not known how to etch porcelain. Although it has been previously known to acid-etch metal, that has been done through an electronic process, which cannot be used with porcelain, a highly insulative material. Heretofore, it was thought porcelain could not be chemically etched and that it would be necessary to in some, as yet unknown, way adapt the acid-etching process for use with porcelain.
The present invention overcomes the deficiencies of the prior practices by the discovery of a method for chemically etching the surface of a porcelain veneer facing which is to be affixed to a tooth, whereby the porcelain facing may be bonded directly to an acid-etched natural or virgin tooth surface by conventional bonding techniques, resulting in a porcelain veneer on a natural tooth with a much stronger and longer lasting bond than was heretofore known or thought possible.
3. Objects of the Invention.
It is therefore a principal object of the present invention to provide a porcelain veneer facing which may be securely affixed to a natural or virgin tooth without significant grinding or reduction of the tooth surface.
Another object of the present invention is to provide a method for acid-etching a selected portion of a porcelain veneer facing.
Another object of the present invention is to provide a method for dental prosthesis comprising a porcelain veneer facing securely affixed directly to a natural or virgin tooth surface by a bonding composition.
Another object of the present invention is to eliminate the shortcomings of the previously conventional techniques for "capping" a discolored or disfigured natural or virgin tooth.
Objects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.
The invention consists in the novel products, arrangements, combinations, steps, processes and improvements herein shown and described.